NOTE: These are
NOT survey grade instruments. However, the newer models have more
accurate receivers than the older models. Handheld GPS receivers
have an instantaneous position accuracy in the clear and at rest of
perhaps 3 to 10 meters (95% confidence). When moving in wooded
terrain, you can expect position excursion of 25/50/ and even hundreds
of feet from the actual position depending on many factors very much
inclusive of the density of the forest and the number of satellites in
view at that moment. My experience with a limited number of
experiments is that you will get within perhaps 10% of the actual area
on a good day. If you need survey grade accuracy, then you must
hire a surveyor. None of the inexpensive GPS receivers can get
you to the centimeter accuracy that some professional gear can attain
under ideal conditions.